Attics Are Not a reception friendly environment and Never Will Be a reception friendly environment. Signal attenuation and signal reflections (multipath) in the attic.
Where is the location of the HD7015??
In the attic or above the roof.
Install the HD7015 above the roof in such a manner that reception is not blocked by roof and house in all directions.
Above the roof aim the HD7015 antenna at about 260 degree magnetic compass direction.
As always , the starting antenna aim direction is the --> starting antenna aim direction.
The aim direction can be adjusted for best reception.
Most Digital Tv's have a signal strength meter and some Digital Tv'
s have a signal quality meter.
Here is how to aim antennas ,
http://www.kyes.com/antenna/pointing/pointing.html.
With the HD7015 antenna above the roof , I suspect that a separate UHF antenna will not be required.
As always , trees and tree leaves do a good job of , reflecting , reducing , blocking , Digital Broadcast reception and so do buildings and other obstructions including your own roof and house.
It is best to install the HD7015 antenna at a location that has the least amount to no amount of obstructions of any type or kind in the directions of reception including your own roof and house.
You could move the Uhf antenna above the roof , however if your are going to do that , then move the HD7015 above the roof.
With the HD7015 above the roof , More Tv stations/channels looks like will be received.
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Yes you can try a Channel Master CM4228HD UHF antenna in the attic or above the roof.
It is fun to Experiment and try.